Labile Dissolved Organic Matter In Riverine Saltmarsh Estuaries: Origins and Biological Utilization

将测量河流盐沼河口溶解有机物（DOM）的生物利用率，并确定其来源，以促进微生物代谢。由于河口的大多数异养活动是由细菌引起的，因此本研究将重点关注细菌使用DOM的来源，以阐明沿海生态系统中能源利用的主要途径。稳定同位素信号将用于确定细菌利用的DOM的最终来源，追踪具有不同稳定同位素组成的河流、盐沼和浮游植物DOM来源的有机物流。为了追踪DOM的使用，已经开发了一种生物测定方法，包括在过滤水中自然细菌的生长，以及随后测定细菌生物量的δ 13C值，在某些情况下，δ 15N。同位素测量将表明所使用的DOM的来源。生物试验中的细菌生长速率和产量表明了不稳定底物来源的营养质量和数量。实验将在马萨诸塞州北部的帕克河扩展到整个年度周期，以确定最终来自浮游植物，米草属植物和高地植物的河口DOM的同位素组成，并通过稳定的同位素示踪测量记录这些有机物来源与细菌生长之间的关系。为了扩大比较和推广研究结果，还将在其他一系列假定有机碳来源大为不同的河口系统中进行更多的实验。这个项目的研究小组很优秀。研究设施是一流的。将进行富有成效的合作。实际上，该研究将为了解河口生物生产力提供相关信息。这类河口的特点往往是脆弱的商业捕鱼业苗圃。

The biological utilization will be measured and the origins will be identified for dissolved organic matter (DOM) fueling microbial metabolism in riverine saltmarsh estuaries. Because most heterotrophic activity in estuaries is bacterial in origin, this research will focus on sources of DOM used by bacteria in order to elucidate a major pathway of energy use in coastal ecosystems. Stable isotope signals will be utilized to identify the ultimate source of DOM used by bacteria, tracing organic matter flow from riverine, saltmarsh, and phytoplankton sources of DOM that have distinct stable isotopic compositions. To trace DOM use, a bioassay has been developed that involves growth of natural bacteria in filtered water coupled with subsequent determination of the delta 13C value of bacterial biomass, and in some cases, delta 15N. The isotopic measurements will indicate the source of DOM utilized. Bacterial growth rates and yields in the bioassay indicate the nutritional quality and quantity of the labile substrate source. Experiments will be extended throughout an annual cycle in the Parker River of northern Massachusetts to determine the isotopic composition of estuarine DOM that is ultimately derived from phytoplankton, Spartina, and upland plants, and to document the relationships between these sources of organic matter and bacterial growth via stable isotopic tracer measurements. Additional experiments will be conducted in a broad suite of other estuarine systems with substantially different presumptive sources of organic carbon in order to broaden the comparison and generalize the research results. The research group for this project is excellent. Facilities for the research are first class. Productive collaborations will be pursued. Practically, the research will provide information pertinent to the understanding of biological productivity of estuaries. Such estuaries are often characterized is the fragile nurseries for the commercial fishing industry.